In association with the recent trend toward diversification and enhanced functionality of various electronic equipment such as video, audio and air-conditioning equipment, there are an increasing number of devices in which a desired function is selected among a variety of functions by turning a switch device to a particular position among several positions. A description of a conventional switch device of this type will be given referring to FIG. 8 and FIG. 9.
FIG. 8 is a perspective view of a conventional switch device. A plurality of wiring patterns (not shown) are formed on the top and rear surfaces of wiring board 1 (hereinafter “board”). Operating member 2 is rotatably mounted on the top surface of board 1. Roughly disc-shaped knob 2A is formed on the top surface of operating member 2 while two or more protruding portions 3A, 3B, 3C, etc., are formed on the outer periphery of the lower part roughly in the form of a gear.
Also, switch 10 has lever 4 and lever 4 protrudes in a swingable manner from case 5 made of an insulating resin. Swinging motion of lever 4 around fulcrum 4A causes a movable contact (not shown) to move into contact with fixed contacts (not shown). Terminals 6A, 6B, 6C are provided for outputting electrical signals from the switch 10.
Switch 10 is laid on the top surface of board 1 in a manner such that lever 4 engages protruding portions 3A, 3B, 3C, etc., of operating member 2. Also, terminals 6A, 6B, 6C are soldered to predetermined wiring patterns and connected with detecting section 7 composed of electronic components including a microcomputer.
The switch device configured as described above is mounted in electronic equipment in a manner such that knob 2A of operating member 2 is disposed in the control section on the front surface of the equipment. And the wiring patterns on board 1 are electrically connected to the electronic circuits of the equipment through a connector and the like.
Operation of the switch device having the above configuration will be described with reference to fragmentary plan views in FIG. 9A to FIG. 9C. In order to switch between functions of the equipment, knob 2A is rotated clockwise by 45°, for example, from the position shown in FIG. 9A. By this rotating operation, operating member 2 is rotated as shown in FIG. 9B and protruding portion 3B pushes lever 4 of switch 10 and lever 4 swings from the neutral position to the left around fulcrum 4A. With this operation, movable contacts housed inside case 5 are moved into or out of contact with fixed contacts, and terminals 6A, 6B, for example, output the electric signals to detecting section 7 and the function of the equipment is switched.
When knob 2A is further rotated clockwise by 45° after protruding portion 3B is detached from lever 4 and lever 4 temporarily returns to the neutral position, lever 4 is pushed by protruding portion 3C to swing again to the left, and the second electric signal is output from terminals 6A, 6B to detecting section 7. Detecting section 7 detects the electric signal from terminals 6A, 6B. Detecting section 7 detects the position of operation of operating member 2 in a manner such that, when an electric signal is output once, detecting section 7 detects that operating member 2 is rotated clockwise by 45°, and when electric signals are output twice, detecting section 7 detects that the operating member 2 is rotated by 90°, and stores the information.
Conversely, when knob 2A is rotated counterclockwise as shown in FIG. 9C from the position in FIG. 9A, operating member 2 is rotated counterclockwise and protruding portion 3A pushes lever 4. Since lever 4 swings to the right as a result of this operation, terminals 6A, 6C output an electric signal to detecting section 7. Detecting section 7 detects the electric signal and determines that operating member 2 is rotated counterclockwise by 45° and stores the information.
That is, depending on whether the pair of terminals 6A, 6B or the pair of terminals 6A, 6C of switch 10 output the signal, detecting section 7 determines the direction of rotation of operating member 2. Also, detecting section 7 determines the angle of rotation based on how many times electric signals are output and stores the information. This type of switch device is disclosed in Japanese Patent Unexamined Publication No. 2001-236861, for example.
In the above-described conventional switch, however, detecting section 7 has always to store the information on how many times knob 2A of operating member 2 is rotated in which direction. Also, when knob 2A is rotated under a state in which the power of the equipment is not on and no power is supplied to detecting section 7, a problem occurs. That is, when the power is turned on next, the position of operation as stored in detecting section 7 does not agree with the actual position of operation of knob 2A. As a result, it becomes necessary to provide some sort of detecting means or to provide correcting means in the electronic circuit, thereby increasing the complexity and cost of the switch device.